Power supply apparatus, image forming apparatus, and integrated circuit

Abstract

The power supply apparatus is configured to detect the output voltage of a piezoelectric transformer and controls the frequency of a pulse signal to drive the piezoelectric transformer based on the detected output voltage and a preset target voltage so as to perform feedback control of the output voltage of the piezoelectric transformer, the gain when performing the feedback control is switched in accordance with the target voltage.

What is claimed is: 
     
       1. A power supply apparatus comprising:
 a piezoelectric transformer configured to output an output voltage; 
 a signal generator configured to generate a signal to drive the piezoelectric transformer; and 
 a controller configured to change a frequency of the signal so that the output voltage from the piezoelectric transformer is to be at a target voltage, 
 wherein in a case where the target voltage is a first voltage, the controller sets a change amount of the frequency of the signal to a first value, and changes the frequency of the signal per the first value in a period from a predetermined frequency to a target frequency corresponding to the first voltage, and in a case where the target voltage is a second voltage less than the first voltage, the controller sets a change amount of the frequency of the signal to a second value larger than the first value, and changes the frequency of the signal per the second value in a period from the predetermined frequency to a target frequency corresponding to the second voltage. 
 
     
     
       2. The power supply apparatus according to  claim 1 ,
 wherein the controller changes the frequency of the signal so that a value corresponding to the output voltage output from the piezoelectric transformer is to be a setting value of the output corresponding to the target voltage. 
 
     
     
       3. The power supply apparatus according to  claim 1 , further comprising a storage unit to store information to determine the first value and the second value. 
     
     
       4. The power supply apparatus according to  claim 3 , wherein the information includes gain values in a PID (proportional-integral-derivative) control, the gain values corresponding to the first value and the second value. 
     
     
       5. The power supply apparatus according to  claim 1 , wherein in a case where the frequency of the signal is changed from the predetermined frequency to the target frequency corresponding to the first voltage, when the piezoelectric transformer is driven according to the signal, the controller changes the frequency of the signal so that the frequency of the signal closes to a resonance frequency corresponding to a maximum value of the output voltage output from the piezoelectric transformer. 
     
     
       6. An image forming apparatus comprising:
 an image forming unit; and 
 a power supply configured to supply a high voltage to the image forming unit; 
 wherein the power supply comprises:
 a piezoelectric transformer configured to output an output voltage; 
 a signal generator configured to generate a signal to drive the piezoelectric transformer; and 
 a controller configured to change a frequency of the signal so that the output voltage from the piezoelectric transformer is to be at a target voltage, 
 wherein in a case where the target voltage is a first voltage, the controller sets a change amount of the frequency of the signal to a first value, and changes the frequency of the signal per the first value in a period from a predetermined frequency to a target frequency corresponding to the first voltage, and in a case where the target voltage is a second voltage less than the first voltage, the controller sets a change amount of the frequency of the signal to a second value larger than the first value, and changes the frequency of the signal per the second value in a period from the predetermined frequency to a target frequency corresponding to the second voltage. 
 
 
     
     
       7. The image forming apparatus according to  claim 6 ,
 wherein the controller changes the frequency of the signal so that a value corresponding to the output voltage output from the piezoelectric transformer is to be a setting value corresponding to the target voltage. 
 
     
     
       8. The image forming apparatus according to  claim 6 , further comprising a storage unit to store information to determine the first value and the second value. 
     
     
       9. The image forming apparatus according to  claim 8 , wherein the information includes gain values in a PID (proportional-integral-derivative) control, the gain values corresponding to the first value and the second value. 
     
     
       10. The image forming apparatus according to  claim 6 , wherein in a case where the frequency of the signal is changed from the predetermined frequency to the target frequency corresponding to the first voltage, when the piezoelectric transformer is driven according to the signal, the controller changes the frequency of the signal so that the frequency of the signal closes to a resonance frequency corresponding to a maximum value of the output voltage output from the piezoelectric transformer. 
     
     
       11. The image forming apparatus according to  claim 6 , wherein the image forming unit includes a charging unit configured to charge an image bearing member, a developing unit configured to develop a latent image formed on the image bearing member, and a transfer unit configured to transfer an image formed on the image bearing member.